fix: do not use a real timeout in waitfor when using fake timers

Author: pierrezimmermann

src/__tests__/waitFor.test.tsx

@@ -204,6 +204,37 @@ test.each([false, true])(
   }
 );
 
+const fibonaci = (n: number): number => {
+  if (n === 0 || n === 1) {
+    return 1;
+  }
+
+  return fibonaci(n - 1) + fibonaci(n - 2);
+};
+
+test.each([false, true])(
+  'it should not depend on real time when using fake timers (legacyFakeTimers = %s)',
+  async () => {
+    jest.useFakeTimers({ legacyFakeTimers: false });
+
+    const mockErrorFn = jest.fn(() => {
+      fibonaci(30);
+      throw new Error('test');
+    });
+
+    try {
+      await waitFor(() => mockErrorFn(), {
+        timeout: 200,
+        interval: 5,
+      });
+    } catch (error) {
+      // suppress
+    }
+
+    expect(mockErrorFn).toHaveBeenCalledTimes(41);
+  }
+);
+
 test.each([false, true])(
   'awaiting something that succeeds before timeout works with fake timers (legacyFakeTimers = %s)',
   async (legacyFakeTimers) => {

src/waitFor.ts

@@ -38,7 +38,7 @@ function waitForInternal<T>(
     let finished = false;
     let promiseStatus = 'idle';
 
-    const overallTimeoutTimer = setTimeout(handleTimeout, timeout);
+    let overallTimeoutTimer: NodeJS.Timeout | null = null;
 
     const usingFakeTimers = jestFakeTimersAreEnabled();
 
@@ -64,6 +64,7 @@ function waitForInternal<T>(
 
         // when fake timers are used we want to simulate the interval time passing
         if (fakeTimeRemaining <= 0) {
+          handleTimeout();
           return;
         } else {
           fakeTimeRemaining -= interval;
@@ -90,6 +91,7 @@ function waitForInternal<T>(
         await new Promise((resolve) => setImmediate(resolve));
       }
     } else {
+      overallTimeoutTimer = setTimeout(handleTimeout, timeout);
       intervalId = setInterval(checkRealTimersCallback, interval);
       checkExpectation();
     }
@@ -98,7 +100,9 @@ function waitForInternal<T>(
       done: { type: 'result'; result: T } | { type: 'error'; error: unknown }
     ) {
       finished = true;
-      clearTimeout(overallTimeoutTimer);
+      if (overallTimeoutTimer) {
+        clearTimeout(overallTimeoutTimer);
+      }
 
       if (!usingFakeTimers) {
         clearInterval(intervalId);